L42. Anatomy of the Lungs and Pleura

Question 1

Define the differences between the parietal pleura and the visceral pleura

Answer 1

The single serous membrane that covers the surface of the lung is the visceral pleura while the parietal pleura is in contact with the structures of the thoracic cavity. They are continuous with one another.

Question 2

What is the importance of the space between these layers?

What happens when there is a break in the integrity of the pleura?

Answer 2

Contain a potential space with a small amount of serous fluid for the frictionless glided movement when breathing.

A break in the integrity leads to pneumothorax (air) or haemothorax (blood) that can limit lung expansion, may cause collapse lung or severe pain.

Question 3

What are the main regions of the parietal pleura and what do they line (4)?

Answer 3

They are named after the parts of the lung that they cover

1. Mediastinal pleura (lines mediastinal/medial surfaces of the lungs)
2. Diaphragmatic (lines the superior aspect of the diaphragm)
3. Costal pleura (lines the internal aspect of the ribs/has grooves)
4. Cervical pleura (forms the dome of the pleura and extends 1-2cm into the neck) - is important in stopping the lungs from rising up too far on large inspiration

Question 4

During quiet inspiration there is not a full filling of the pleura and only fills in active/full inspiration. What is the unfilled area called? Where is it and what is its significance?

Answer 4

The Costodiaphragmatic recess that only fills during large inspiration.

It is in the lateral corners of the pleural cavities and it is important because it is the first place that fluid fills in pneumothorax (under gravity)

Question 5

Where is the suprapleural membrane and why is it important?

Answer 5

The suprapleural membrane is a membrane that functionally and physically separates the thoracic wall from the structures of the neck.
It is important as it stops the lungs from going up through the superior aperture into this space.

Question 6

Where is the pleural cavity exposed posteriorly?

Answer 6

Beneath the 12th rib

Question 7

Where is the hilum and what is it?

What structures lie within the lung route/hilum?

Answer 7

The hilum is on the medial aspect of each lung that carries all major vessels to and from the lungs.

• Bronchi
• Arteries and Veins
• Lymphatics

Question 8

Is the hilum a tightly fitting area? Why is this important?

Answer 8

No
The hilum is a loose hanging sac-like structure surrounding the vessels of the lung root, this slack that hangs off the bottom is called the PULMONARY LIGAMENT and is a double fold of pleura hanging down from the structures.

It is important because vessels (particularly the veins) are capacitance vessels and need to be able to expand on demand.

Question 9

What is the difference in pain perception between the visceral and parietal pleura?

Answer 9

The visceral pleura has very DULL and POORLY LOCALISED pain because the pleura shares innervation with the pericardium and the peritoneum.

The parietal pleura has a very SHARP, SEVERE and LOCALISED pain because it has somatic nerve supply

Question 10

Where does the trachea begin and how does it descend?

Answer 10

The trachea begins in the neck at the level of C6 and descends inferiorly trough the thoracic inlet into the superior mediastinum.

Question 11

What level does the trachea bifurcate into the right and left main bronchi? Which section of mediastinum is this?

Answer 11

Bifurcates at the level of T4-5 into the right and left main bronchi in the superior mediastinum.

Question 12

What is the difference between the right and left main bronchi into the lungs? How does this explain the likely site of lodgement for swallowed objects?

Answer 12

The right bronchi is shorter and wider and more vertical than the left. Thus if a person inhaled something then it is more likely to lodge in the right bronchi under the force of gravity

Question 13

What keeps the trachea constantly patent?

What is the posterior muscle of the trachea called?

Answer 13

Has a series of hyaline cartilage C-shaped structures that keeps the trachea patent at all times. At the posterior end the trachea is enclosed by the TRACHEALIS muscle that enables the lumen of the trachea to be changed.

Question 14

Describe the generation of the bronchial tree

What is the significance of segmental bronchial airways on the lungs?

Answer 14

The right and left main bronchi enter the lungs through the hilum and from there they give rise to LOBAR bronchi each supplying one lobe of the lung. These separate into SEGMENTAL bronchi.

This means that pathology to one part of the lung is usually limited to that segment. It is also important for surgical resections of the lungs without impacting the functioning of other sections

Question 15

How are the segments shaped and how is this shape orientated? How many segments are there?

Answer 15

There are 10 segments in each lung that are shaped like pyramids. The bases form the outer surface of the lungs and the tips of the pyramids meet at the hilum

Question 16

What is the significance of the segmental bronchi to applied anatomy and mucous drainage?

Answer 16

When a patient has pneumonia/pathology in one or two segments, physicians would position the patient so that gravity would aid in draining the mucous out (the segmental bronchi in question would be vertical and pointing down.

Question 17

What happens when a person vomits or has fluid in the lungs in the supine position?

Answer 17

Due to the orientation of the bronchi, when lying down the apical segment of the lower lobe is vertical and hence fluid accumulates in this area and this is the area to first examine (auscultate)

Question 18

Describe the main lung surfaces and their concavity and major features

Answer 18

The inferior surface of the lung is always concave with the diaphragm
The apex protrudes above the level of the first rib and clavical
The costal surface is rounded and has imprints of the ribs on it
The mediastinal surface contains the hilum and imprints from mediastinal structures

Question 19

Is the right lung larger or smaller than the left?

How many lobes and fissures are in the right lung? What are they called and where are they located?

Answer 19

The right lung is larger than the left (doesn’t have the heart)
It contains 3 lobes: Superior, middle and inferior which are divided by the horizontal and oblique fissures.

Question 20

How many lobes and fissures does the left lung have? What are they called and where are they located?

Answer 20

The left lung has 2 lobes: superior and inferior separated by the left oblique fissure

Question 21

Describe the upper lobe of the left lung and how it is important

Answer 21

The upper lobe of the left lung has a ‘cut out’ imprint formed by the lateral border of the left ventricle of the heart:
Upper Lobe, The Cardiac Notch and the Lingular (functional correlate of the right middle lobe)

Question 22

What are the depths of the major structures in the hilum? The airways vs. the pulmonary arteries vs. the pulmonary veins

Answer 22

Pulmonary arteries are always anterior and superior
The bronchi are inferior and posterior
The pulmonary veins (2 going coming out of each) one is always anterior and one is always inferior

Question 23

What is the difference between the right and left hilar structures?

Answer 23

The bronchi: The right bronchus divides before it enters the lung while the left doesn’t. This means the right hilum has 2 bronchi going into it.
What the bronchi does, the pulmonary arteries do and thus two pulmonary arteries also enter the lungs on the right hand side.

Question 24

What is the bronchus intermedius?

Answer 24

The right main bronchus divides into the bronchus intermedius and changes its name into this.

Question 25

Describe the medial surface of the lung and the imprints made on them.
Which imprint is more prominent on the medial surface of the right lung, the SVC or the IVC? Why?

Answer 25

RIGHT: has venous structures (SVC, rarely IVC [because it directly plugs from the diaphragm into the atria], azygous vein) and the right atrium
LEFT: The left ventricle, the main arteries (hence a much larger imprint)

Question 26

What are the other, smaller structures running through the hilum?

Answer 26

The lung tissue itself requires oxygenation and so smaller bronchial arteries and veins also enter and leave the hilum. Other nerves and lymphatics also run through the hilum.

Question 27

Describe the lymphatic channels in the hilum

Answer 27

Often stained black due to carbon and other pollutant accumulation.

They are scattered through the hilum

Question 28

How many bronchial arteries exist and where do they arise?

Answer 28

Usually 3-5 (varies from person to person)
Arise from the anterior surface of the descending aorta and delivers blood to the bronchial tree and interstitial lung tissues.

Question 29

Where do the bronchial veins empty?

Answer 29

Into the azygous system

Question 30

What are the two systems of lymphatics to the lungs? Where do they meet?

Answer 30

Superficial and Deep which meet at and drain into the the hilar lymph nodes.

Question 31

Describe the outermost system of lymphatics of the lungs, what it looks like, where it lies on

Answer 31

The superficial system has a reticulated pattern (looks like a spiderweb) and lies immediately beneath the visceral pleura.

Question 32

Describe the inner system of lymphatics of the lungs, how they are arranged and where they empty into

Answer 32

These follow the airways and blood vessels and collect lymph from deep in the lung and carry it to the hilum

Question 33

What lymph nodes do the hilar lymph vessels form? Where do they ultimately lead to?

Answer 33

The hilar lymph nodes form the tracheal-bronchial lymph nodes and broncho-medial trunks. From there they drain to the thoracic duct and right lymphatic channel.

Question 34

What does the autonomic nerve supply to the lungs achieve?
Where does sympathetic innervation arise?
Where does parasympathetic innervation arise?

Answer 34

Autonomic: regulates airway diameter and mucous production
Sympathetic: from the ganglia of the sympathetic trunk that regulate tone and the diaphragm
Parasympathetic: from the vagus nerve (before the formation of the oesophageal plexus)